Switch and contact arrangement



Nov. 11, 1969 0, PE ET AL 3,478,185

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United States Patent 3,478,185 SWITCH AND CONTACT ARRANGEMENT Gordon 0. Perkins, Flossmoor, and Howard E. Swanson, Chicago, Ill., assignors to G & W Electric Specialty Company, Blue Island, 11]., a corporation of Illinois Filed Oct. 31, 1967, Ser. No. 679,335 Int. Cl. H01h 3/00, 9/00 US. Cl. 200166 6 Claims ABSTRACT OF THE DISCLOSURE The invention relates to an improved switch and contact arrangement and has reference more particularly to switch blade structure capable of controlling currents of high amperage.

The improved switch and contact arrangement of the invention has been designed to close and open electric circuits and which while remaining closed, or upon closing the circuits may momentarily carry currents up to at least a 40,000 RMS ampere level. In order to be commercially acceptable such switches must withstand such currents without any mechanical or thermal damage and said switches must thereafter operate in a satisfactory manner in controlling their rated load currents. In order to accomplish this objective the present switch arrangement embodies a new and improved form of movable switch structure and also employs flexible conductors at the pivot connection of the movable switch structure, the flexible conductors connecting the movable switch contacts with the stationary current supply terminals. Use of the flexible conductors eliminates contact damage due to mechanical shock during close-into-fault operations and said flexible conductors also eliminate the need for costly alignment procedures and tolerance requirements.

Another objective of the invention is to provide switch blade structure while will employ multiple shoes so as to double the points of contact and thereby reduce the heating of each contact point since the same is required to carry less current. Multiple shoes improve the chance that engagement between the moving and stationary contacts will be maintained when closing into the fault and when mechanical bounce is prevalent.

Another object is to provide switch blade structure which will employ a braid restraining plate to backup the flexible braid. The plate accordingly restricts the motion of the braid so that when the braid flattens against the plate it becomes equivalent to a rigid member and does not further open up due to electromagnetic forces and which would cause a reduction in the electromagnetic component of contact pressure.

A further and more specific object resides in the provision of pregapped contacts in a switch and contact arrangement of the character described. Pregapping is used in the present switch to reduce the amount of contact movement required of the shoes to spread onto the stationary contact.

With these and various other objects in view the invention may consist of certain novel features of construction and operation as will be more fully described ice and particularly pointed out in the specification, drawings and claims appended thereto.

In the drawings which illustrate an embodiment of the device and wherein like reference characters are used to designate like parts- FIGURE 1 is a sectional view through the oil containing tank showing in elevation the improved swtich and contact arrangement of the invention, the movable switch contact being shown in open position with respect to the stationary contact;

FIGURE 2 is an elevational view of the contact structure showing the movable contact in engaged relation with the stationary contact; 7

FIGURE 3 is an end view of the contact structure of FIGURE 2. with the stationary contact being omitted;

FIGURE 4 is an end view of the contact structure of FIGURE 3 but showing the shoes in minimum spaced relation as permitted by the pregap plates;

FIGURE 5 is a top plan view of the contact structure shown in FIGURE 3, with the contact shoes in maximum spaced relation;

FIGURE 6 is a sectional view taken substantially on the line 6-6 of FIGURE 5 and showing in detail the arrangement of the various parts making up the movable contact;

FIGURE 7 is an elevational view of one of the shoes of the movable contact;

FIGURE 8 is a top plan view with parts being shown in section of the shoe illustrated in FIGURE 7; and

FIGURE 9 is a fragmentary elevational view showing the pivot shaft at one end of the switch contact structure.

FIGURE 1 of the drawings shows a single break oil switch for polyphase circuits and wherein the movable switch blades, which embody the improvements of the invention, have pivotal movement in an arc between open circuit position and closed circuit position. The switch structure is located within the oil containing tank 10 having a bottom wall 11, a top Wall 12 and side walls 13 and 14. Supports such as 15 mount and support the tank 10 from the supporting structure 16. The top wall 12 is provided with a filling plug 17 and the valved drain 18 depends from the bottom wall 11.

The stationary current supply conductor assembly 20 extends through the bottom Wall of the tank being suitably insulated from the tank in the conventional manner and being also insulated within the tank since the conductor extends through the bushing 21 to project from the top end thereof. The flexible conductor 22 is electrically connected to the conductor assembly 20 by the clamp 23 and said flexible conductor provides a flexible electrical connection between the stationary conductor 20 and the movable switch structure indicated in its entirety by the numeral 24. The switch structure is supported by the pivot shafts 25 for pivotal movement, FIG- URE 9, and said switch structure includes the movable switch contacts 26 which are adapted to coact with the stationary contact 27 to control the flow of the electric current through the tank, FIGURE 1.

The circuit for the flow of the electric current through the tank including the conductor 20, the movable contacts 26 and the stationary contact 27, also includes the bus bars 28 to which the stationary contact 27 is secured. The said bus bar is in turn mounted on and supported from a side wall of the tank by the mounting bracket 30 with the standoif insulator 31 being interposed in the mounting structure. The circuit is completed by the conductor 32 which electrically connects with the bus bar 28 and extends through the top wall of the tank, being insulated both inside and outside the tank by the bushing 33.

Pivotal movement is imparted to the movable switch structure 24 by actuation of the pivot shaft 25 through the connecting linkage 35 and 36. The use of flexible conductors such as the braids 22 at the pivotal joints between the stationary and movable parts of the switch arrangement materially simplifies the structure involved. If mechanical means were to be used then close tolerances and fine adjustments of the parts would present serious problems. With the use of the flexible conductors these problems are eliminated and in addition the flexible conductors provide for a total rotation of at least 180 degrees which is more than adequate for the present arrangement and permits accommodating at least three stationary contact positions in the enclosure at the same time which can be connected individually to a power source or sources as desired.

One or more movable switch structures may be mounted on and actuated by the wooden struts 38. The end plate members 37 are connected by the wooden struts 38 which are disposed on respective sides of each insulator 40. The struts 38- and the insulators 40 interconnect by reason of the recesses in the insulators and thus the assembly is a unitary one and as a result of which all the insulators are pivotally mounted by the pivot shafts 25, FIGURE 9.

In FJGURE 3 the flexible conductors 22 are shown as electrically connected by the securing units 41 to the copper terminals 42 which are encased in the insulator 40 and bifurcated at its upper end for connecting with the improved contact structures. The improved contact structures and which includes contact shoes are mounted on the projecting ends of the terminals 42 as will now be described.

The terminals 42 are spaced a predetermined distance so that the contact shoes 46 will be properly spaced for receiving between the shoes the stationary contact 27 and for applying the required pressure tothe stationary contact. Each terminal carries a pair of shoes 46 having the shape as best shown in FIGURES 7 and 8. The central portion of the shoe provides a flat contact surface 47. On the opposite surface the shoe is recessed at 48 and each end portion 50 of the shoe is apertured at 51.

The securing screws 52 fixedly secure to the extending portion of each terminal 42 a gap plate 53, a length of flexible braid 54 and a backup or restraining plate 55. These three elements are secured to the outer surface of the terminal with the securing screws being anchored in the terminal. On the inside surface of each terminal there is located a pair of shoes 46 and each shoe is yieldingly biased in an inward direction away from the terminal by a spring member 56. Each shoe retains its own spring member since the member is positioned in the recess 48 of the shoe. It will also be observed that each shoe is retained by being secured to the flexible braid. Each end portion 50 is secured by a screw 57 to a pregap plate 58 and to a clamp plate 60 with the flexible braid 54 being interposed and clamped therebetween. By comparing FIGURE 4 with FIGURE the extent of movement of a shoe as permitted by the gap and pregap plates can be observed.

FIGURE 4 shows the switch contact structure in the position the parts assume when out of engagement with the stationary contact 27. The shoes under the action of the springs 56 are moved inwardly towards each other to narrow the gap between the oppositely disposed shoes. This inward movement is limited by the gap plate 53 and by the pregap plate 58. In FIGURE 4 it will be seen that the shoes have moved inwardly towards each other to an extent to cause the plates 58 to contact plate 53. It will, of course, be understood that such movement is permitted since the shoes are fixed to the flexible braid 54.

In FIGURE 5 the oppositely disposed contact shoes are shown in the position they assume when in engagement with the stationary contact 27. The shoes have moved outwardly away from each other to an extent as permitted by the pregap plates 58 which are long enough to overlap both the gap plate 53 and also the restraining or backup plate 55. It will be observed in FIIGURE 5 that the braid 54 is flat and is disposed in a straight line from end to end.

The use of a backup plate to restrict the motion of the flexible braid is an important feature. When the braid flattens against the plate it becomes equivalent to a rigid member and does not open up further to reduce the component of contact pressure due to the electromagnetic forces. This has the eflect of maximizing the contact forces available. Thus the present construction provides increased force only when high current is flowing which, is the only time the increased force is needed.

The pregapping which is provided for in the present switch contacts serves to limit the movement permitted of the shoes to spread onto the stationary contact. The greater the distance the shoes are allowed to move, the greater the amplitude or bounce gap that can be expected when the moving contact shoes engage or strike the stationary contact. This feature also helps to prevent the formation of any arc that might be formed which would be detrimental to the material of the shoes.

The use of multiple shoes increases the number of points of contact so that there is less heating of each point and thus less heating of the shoes due to having less current transferred through each one. Also, if any one shoe is engaged there will be no arcing across the remaining shoes even though air gaps may be present since there is no difference of potential between the moving and stationary contacts. Thus multiple shoes improve the chance that some contact between the moving and stationary contact will be maintained when closing into the fault and when mechanical bounce is prevalent.

The invention is not to be limited to or by details of construction of the particular embodiment thereof illustrated by the drawings, as various other forms of the device will, of course, be apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

1. In switch contact structure, the combination with a pair of spaced metal terminals having connection with a source of electric current, of at least one contact shoe carried by each terminal, each contact shoe having a flat contact surface and which is directed to one side of the terminal in opposed relation to the flat contact surface of the other shoe, a restraining plate fixed to each terminal on the side opposite the shoe, a length of flexible braid also fixed to each terminal by being interposed between the terminal and said restraining plate, said flexible braid projecting beyond the respective side edges of its restraining plate, individual means securing the ends of each shoe to the projecting portions respectively of the flexible braid for its particular terminal, and a spring member between each shoe and its terminal tendilillg to bias the shoe inwardly and towards its opposite s 0e.

2. Switch contact structure as defined by claim 1, wherein two contact shoes are mounted on each terminal one above the other, wherein a spring member is provided for each contact shoe, and wherein both contact shoes for each terminal are secured at their respective ends to the flexible braid for their particular terminal.

3. Switch contact structure as defined by claim 1, additionally including a pregap plate fixed to each shoe at the respective ends thereof, and also including means fixed to the terminal for each shoe for coacting with the pregap plates thereof whereby to limit the movement of the shoe inwardly as urged in said direction by the spring member of the shoe.

4. In switch contact structure, the combination with a pair of spaced metal terminals having connection with a source of electric current, of at least one contact shoe carried by each terminal, each contact shoe having a flat contact surface and which is directed to one side of the terminal in opposed relation to the flat contact surface of the other shoe, a restraining plate fixed to each terminal on the side opposite the shoe, a length of flexible braid also fixed to each terminal by being interposed between the terminal and said restraining plate, said flexible braid projecting beyond the respective side edges of its restraining plate, individual means securing the ends of each shoe to the projecting portions respectively of the flexible braid for its particular terminal, a spring member between each shoe and its terminal tending to bias the shoe inwardly and towards its opposite shoe, a gap plate fixed to each terminal and being interposed between the terminal and the flexible braid for said terminal, and a pregap plate fixed to the ends of the shoes respectively and located between the shoe and the flexible braid, said pregap plates having coacting relation with the gap plate for their terminal to limit the inward movement of the shoe as urged in said direction by the spring member.

5. Switch contact structure as defined by claim 4, wherein the coacting relation which the pregap plates 6 have with the gap plate is due to the overlapping relation which the plates have with each other.

6. Switch contact structure as defined by claim 4,

Wherein the pregap plates have overlapping relation with t the gap-plate and also with the restraining plate for their particular terminal.

References Cited UNITED STATES PATENTS 882,388 3/ 1908 Hilliard et a1. 2,286,131 6/1942 Wallace et a1 200-48 2,293,652 8/ 1942 Johnson 200-48 2,300,893 11/1942 Hayford.

2,367,937 1/ 1945 Gates 200-146 2,469,203 5/1949 Palme et a1. 200-146 H. O. JONES, Primary Examiner US. Cl. X.R.

5233 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. id-7 5 Dated December I 9 9' Inventor(s) Gordon 0. Perkins and .Howard E. Swanson It 15 certified that error appears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 2, line 16, "an end view" should be -a ,top plan-- SIGNED AND SEALED FEB 2 4 1970 Ame V mm n. ma. 1 r M mm. am, xmn prfim m Paige: 

